{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T03:03:46Z","timestamp":1760151826499,"version":"build-2065373602"},"reference-count":25,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2022,9,12]],"date-time":"2022-09-12T00:00:00Z","timestamp":1662940800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>In this paper, we study two types of second-order nonlinear differential equations with variable coefficients and mixed delays. Based on Krasnoselskii\u2019s fixed point theorem, the existence results of positive periodic solution are established. It should be pointed out that the equations we studied are more general. Therefore, the results of this paper have better applicability.<\/jats:p>","DOI":"10.3390\/e24091286","type":"journal-article","created":{"date-parts":[[2022,9,12]],"date-time":"2022-09-12T22:53:46Z","timestamp":1663023226000},"page":"1286","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Positive Periodic Solution for Second-Order Nonlinear Differential Equations with Variable Coefficients and Mixed Delays"],"prefix":"10.3390","volume":"24","author":[{"given":"Zejian","family":"Dai","sequence":"first","affiliation":[{"name":"School of Mathematics and Statistics, Chaohu University, Chaohu 238024, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4484-8789","authenticated-orcid":false,"given":"Bo","family":"Du","sequence":"additional","affiliation":[{"name":"School of Mathematics and Statistics, Huaiyin Normal University, Huaian 223300, China"}]}],"member":"1968","published-online":{"date-parts":[[2022,9,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"110","DOI":"10.1016\/j.aml.2006.02.028","article-title":"Periodic solutions for a second order nonlinear functional differential equation","volume":"20","author":"Wang","year":"2007","journal-title":"Appl. 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